The life cycle of the brown alga Ectocarpus involves an alternation between two multicellular generations, the gametophyte and the sporophyte. When the IMMEDIATE UPRIGHT (IMM) gene is mutated, the sporophyte generation loses its extensive basal system and adopts a developmental pattern more similar to that of the gametophyte. The mutant exhibits no phenotype during the gametophyte stage suggesting that the deployment of the extensive basal system, directed by IMM, is an evolutionary innovation specific to the sporophyte generation. Identification of the IMM gene revealed that it is a member of a large, rapidly evolving family of genes, which was called the EsV-1-7 domain family. EsV-1-7 domain genes exhibit an unusual distribution across the eukaryotic tree of life and were found in several viral genomes, suggesting horizontal transfer between eukaryotic lineages, perhaps mediated by viruses. IMMEDIATE UPRIGHT (IMM) is the first macroalgal developmental gene to have been identified by a forward genetic approach and therefore represents a major step towards the emergence of macroalgal developmental biology.
Nicolas Macaisne, Fuli Liu, Delphine Scornet, Akira F. Peters, Agnieszka Lipinska, Marie-Mathilde Perrineau, Antoine Henry, Martina Strittmatter, Susana M. Coelho, J. Mark Cock (2017). The Ectocarpus IMMEDIATE UPRIGHT gene encodes a member of a novel family of cysteine-rich proteins with an unusual distribution across the eukaryotes. Development 2017 144: 409-418; doi: 10.1242/dev.141523
Development "In this Issue". Evolving an atypical developmental programme with IMM. Development 2017 144: e0301
Article in The Node. http://thenode.biologists.com/people-behind-papers-12/interview/